Why Doesn’t Physics Help Us to Understand the Flow of Time?
Why Read This
What Makes This Article Worth Your Time
Summary
What This Article Is About
Gene Tracy, Chancellor Professor of Physics Emeritus at William & Mary, examines the profound disconnect between our visceral experience of time’s flow and modern physics’ mathematical descriptions. While time’s passage from past to future dominates human consciousness, physics treats time as merely another dimension in an eternalised “block universe” where everything exists simultaneously. Tracy explores how Newtonian and Einsteinian theories, along with quantum mechanics, operate under time-symmetric laws that look identical running forward or backward.
Drawing on personal memories, cognitive science, and competing theoretical frameworks from physicists like Lee Smolin and Julian Barbour, Tracy suggests our experience of time’s flow may be a cognitive construct—a story the brain tells using memories arranged according to the thermodynamic arrow of entropy. He argues that both scientific theorizing and storytelling emerge from the same existential drive: our fear of mortality and yearning for permanence, revealing that the question of time ultimately connects mathematical physics with the most fundamental aspects of human existence.
Key Points
Main Takeaways
The Block Universe Problem
Modern physics treats time as a static dimension where past, present, and future coexist eternally, contradicting our lived experience of flowing time.
Time-Symmetric Physics
Fundamental physical laws work identically whether time runs forward or backward, providing no explanation for why we remember past but not future.
Brain as Storyteller
Our perception of time’s flow may be a cognitive construct—the brain creating coherent narratives from chaotic sensory data and memories arranged by entropy.
The Entropy Connection
We remember past but not future because memories align with entropy’s arrow—toward increasing disorder—making forward-time memories stable and backward-time ones impossible.
Competing Frameworks
Physicists like Smolin argue time’s flow is real and fundamental, while Barbour proposes time itself is illusion—merely coherent threads through static moments.
Existential Underpinning
Scientific theorizing and personal storytelling both emerge from humanity’s fear of death and desire for permanence, revealing deep connections between physics and meaning.
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Article Analysis
Breaking Down the Elements
Main Idea
The Physics-Experience Disconnect
Modern physics has created increasingly sophisticated mathematical descriptions of time while systematically excluding the most fundamental aspect of temporal experience—its directional flow from past to future. This disconnect suggests either that physics is incomplete or that our subjective experience of time reflects cognitive processes rather than fundamental reality, raising profound questions about consciousness, memory, and the relationship between scientific knowledge and lived experience.
Purpose
To Examine and Bridge
Tracy aims to illuminate the gap between physics’ mathematical formalisms and human temporal experience, advocating for approaches that acknowledge both domains’ validity. By interweaving personal narrative with theoretical physics, he argues that scientific inquiry and storytelling share existential roots, ultimately suggesting that understanding time requires recognizing how subjective experience and objective description inform each other rather than treating them as fundamentally separate realms of inquiry.
Structure
Personal Memoir → Theoretical Survey → Philosophical Synthesis
Tracy begins with intimate memories establishing the experiential reality of time’s flow, transitions through examination of how Newton, Einstein, quantum mechanics, and contemporary theorists handle temporality, then synthesizes these perspectives through cognitive science and philosophy. The structure mirrors the article’s argument: starting from immediate human experience, moving through abstract theoretical frameworks, and returning to lived experience enriched by theoretical understanding, demonstrating how scientific and narrative knowledge ultimately converge around existential concerns.
Tone
Reflective, Philosophical & Elegiac
Tracy maintains a contemplative, meditative tone that interweaves technical exposition with deeply personal reflections on mortality and memory. His voice is elegiac—mourning the disconnect between physics and experience while celebrating the human capacity to construct meaning through both mathematics and narrative. The tone acknowledges physics’ limitations without dismissiveness, presenting complex theoretical debates accessibly while preserving their philosophical weight and existential significance.
Key Terms
Vocabulary from the Article
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Tough Words
Challenging Vocabulary
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The four-dimensional continuum combining three spatial dimensions and one time dimension, forming the fabric of the universe in Einstein’s relativity.
“The spacetime continuum itself, so beloved of Star Trek’s Mr Spock, is an invariant stage upon which the drama of the world takes place.”
Relating to the branch of physics concerned with heat, energy, and their transformations, particularly the laws governing energy transfer in systems.
“Any physical thing that has the characteristics of a memory will tend to align itself with the thermodynamic arrow of time.”
Lasting for an indefinitely long time; enduring or continually recurring across years or throughout all seasons without cessation.
“It is an insight that has borne tremendous fruit, yet one that counsels perennial humility.”
Inherent preferences or tendencies toward particular attitudes, choices, or behaviors, often influenced by past experience or biological disposition.
“Memories are a kind of story our brain creates, formed from the clay of sensory input, sorted into patterns based upon our past life experience, guided by predilections we have inherited in our DNA.”
Having the shape or properties of a parabola; following a curved path that is symmetrical around a central axis, like a thrown ball.
“As a physicist, I know the ball followed a smooth parabolic trajectory from start to finish.”
In a manner impossible to stop or prevent; continuing relentlessly forward without any possibility of being altered, reversed, or halted.
“What language can take us into the heart of the atom and beyond the edge of the galaxy, and describe the passage of time that pulls the world inexorably forward on these scales?”
Reading Comprehension
Test Your Understanding
5 questions covering different RC question types
1According to the article, the fundamental laws of physics in Newton’s mechanics, Einstein’s relativity, and quantum mechanics all look identical whether time runs forward or backward.
2According to Mlodinow and Brun’s theory discussed in the article, why do we remember the past but not the future?
3Which sentence best captures Tracy’s view on the relationship between scientific theorizing and storytelling?
4Evaluate these statements about theoretical perspectives on time discussed in the article:
Lee Smolin argues that scientists should accept time’s flow as fundamentally real and build new physics upon that foundation.
Julian Barbour’s “Heap” theory proposes that time exists but flows in both directions simultaneously.
Richard Feynman’s “sum over histories” interpretation suggests particles travel along all possible paths simultaneously.
Select True or False for all three statements, then click “Check Answers”
5Based on Tracy’s discussion of how our experience of “now” is constructed, what can we infer about the relationship between perception and reality?
FAQ
Frequently Asked Questions
A block universe is the conception arising from Einstein’s relativity where time functions as a dimension similar to space, with past, present, and future all existing simultaneously as an invariant four-dimensional spacetime continuum. This conflicts with our experience because we viscerally feel time flowing from past to future, with the present moment seeming uniquely real and accessible while past and future appear fundamentally different—yet the block universe treats all temporal moments as equally existing.
Entropy measures disorder in physical systems and tends to increase over time in closed systems—this tendency defines the thermodynamic arrow of time. Mlodinow and Brun argue that any physical system with memory characteristics naturally aligns with this arrow because memories of the past are dynamically stable (consistent with increasing entropy) while memories of the future would be unstable (requiring entropy to decrease). This makes remembering the past but not the future statistically necessary rather than mysterious, even though microscopic physical laws are time-symmetric.
Julian Barbour proposes that time itself is illusory and the universe consists of a collection of static moments—”The Heap”—like unsorted photographs in a shoebox. Each moment contains a complete snapshot of the entire universe with implicit references to all other moments. Following coherent threads through these moments creates the experience of time’s flow. Most threads are incoherent nonsense, but rare mutually coherent families of threads tell sensible stories with consistent memories, and we experience these robust, self-reinforcing pathways as temporal progression.
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This article is classified as Advanced difficulty because it requires understanding sophisticated theoretical physics concepts like spacetime continuums, quantum mechanics, and thermodynamic entropy while navigating complex philosophical arguments about consciousness and reality. It employs specialized vocabulary, references multiple theoretical frameworks from different physicists, and demands sustained attention to abstract reasoning that moves between personal narrative, scientific exposition, and philosophical synthesis. The article assumes readers can hold multiple competing theories in mind while evaluating their implications.
Tracy uses personal memories strategically to demonstrate his central argument: that subjective temporal experience and objective physical theory both arise from the same existential concerns. The memories establish the experiential reality of time’s flow that physics fails to capture, while simultaneously illustrating how memory itself operates according to the principles being discussed—organized by entropy, constructed narratively, driven by mortality awareness. This structural choice embodies his thesis that scientific theorizing and storytelling are fundamentally connected rather than separate modes of understanding.
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